A large number of anti-aging skin care ingredients are phenolic in nature. Many of these function as anti-oxidants or skin illuminating ingredients, and the free hydroxyl groups are key to the redox activity of these species. Unfortunately, many of these materials have physical properties that are not well-suited for use as cosmetic ingredients; they tend to have minimal solubility in most cosmetic solvents (both oils and water) and can be unstable in a cosmetic formulation (particularly towards oxidation). Derivatization of the phenolic groups can stabilize these materials. However, these derivatives must be readily removable under physiological conditions to liberate the phenolic groups to afford the desired anti-aging activity (Grasso et al, Bioorganic Chem. 2007, 35, 137-152).
Derivatization of the phenolic groups can vastly improve the physical properties of these materials. One useful method for derivatization of hydroxyl or carboxyl-containing materials is to prepare esters of these materials. The usefulness of this approach often depends upon the ability of enzymes in the skin to hydrolyze these esters to liberate the parent active. This strategy is effective for the derivatization of many active ingredients containing aliphatic alcohols, but esters derived from phenols are often refractive or only slowly reactive towards enzymatic hydrolysis. Despite this, there has been interest in ester derivatives of phenolic active ingredients such as resveratrol (composition of matter patents: U.S. Pat. No. 6,572,882 and US Patent Appl 2009/0068132 A1; formulation patents: US Patent Appl 2009/0035236 A1, US Patent Appl 2009/0035237 A1, US Patent Appl 2009/0035240 A1, US Patent Appl 2009/0035242 A1, and US Patent Appl 2009/0035243 A1) and hydroxytyrosol (U.S. Pat. No. 7,098,246 and US Patent Appl 2003/0225160), even though the hydrolysis to release the parent phenolic active ingredient is questionable. Indeed, with hydroxytyrosol the aliphatic hydroxyl group is often the only functionality esterified (Grasso et al, Bioorganic Chem. 2007, 35, 137-152; Trujillo et al, J. Agric. Food Chem. 2006, 54, 3779-3785; Mateos et al, J. Agric. Food Chem. 2008, 56, 10960-10966; Gordon et al, J. Agric. Food Chem. 2001, 49, 2480-2485; Buisman et al, Biotechnology Lett. 1998, 20, 131-136; US Patent Appl 2005/015058 A1; Fr. Demande 2,919,800; ES 2,233,208; ES 2,246,603), leaving the phenolic groups underivatized, which will not improve the stability of the catechol functionality. Alkyl carbonate derivatives of these phenolic skin care active ingredients have not been described.
Novel derivatives of phenolic actives that will hydrolyze under physiological (enzymatic) conditions would be of great utility and interest.